1. Field of the Invention
The present invention relates to a method, system, and program for managing a speed at which data is transmitted between network adaptors.
2. Description of the Related Art
In a network environment, a network adaptor card on a host computer, such as an Ethernet card, Fibre Channel card, etc., will receive Input/Output (I/O) requests or responses to I/O requests initiated from the host. Often, the host computer operating system includes a device driver to communicate with the network adaptor, and provide an interface between the host operating system and the network adaptor.
When two Ethernet cards communicate over a network, they both engage in an auto-negotiation protocol to select a highest possible common mode speed at which both are capable of communicating, such as 10 megabits per second (Mbps), 100 Mbs, 1000 tyros, half duplex, full duplex, etc. During auto-negotiation, the Ethernet devices transmit a series of link pulses that advertise their capabilities to the other device that shares the link segment. Devices transmit a Link Code Word (LCW) that is encoded with the device transmission capabilities. The hardware in the Ethernet cards is configured to select the highest common speed between the two devices based on the capabilities communicated in the link pulses. Further details of the auto-negotiation process to select a highest common speed between two network devices is described in the publication IEEE Standard 802.3-2002 (Copyright by the institute of Electrical and Electronic Engineers (IEEE), 2002), which publication is incorporated herein by reference in its entirety.
With prior art Ethernet auto-negotiation, the two linked devices communicate at the highest common speed, regardless of whether the highest speed is needed. Transmissions at higher speeds consume greater power than lower speed transmissions. Moreover, devices may be consuming additional power to transmit at the highest common link speed when such high speeds are not needed. For instance, lower speed transmissions may be sufficient when checking electronic mail or “surfing” the Internet. Power conservation may be especially important for battery powered computing devices, such as laptops, hand held computers, etc., and computers deployed in an energy conservation sensitive environment.
For these reasons, there is a need in the art to provide improved techniques for managing the transmission speed between network devices.